Fuel feed device for an injection engine



United States Patent lnventors Francois Jules Marie Gastinne FUEL FEEDDEVICE FOR AN INJECTION ENGINE 3 Claims, 2 Drawing Figs.

123/139,123/179,123/187.5 Int. Cl. ..F02m 59/00 Field ol'Search...123/136,

Primary Examiner-Laurence M. Goodridge Attorney-Burns, Doane, Benedict,Swecker & Mathis ABSTRACT: Fuel feed device comprising, located betweena fuel feed tank and an injection pump, a low-pressure pump and ahigh-pressure pump. The low-pressure pump inlet is connected to the tankand the outlet is connected to the top of a chamber affording a pressurehead. The high-pressure pump inlet is connected to a fuel takeotf pointat the bottom of the chamber and its outlet is connected to theinjection pump. The high-pressure pump output exceeds the injection pumpoutput and the chamber volume above the takeoff point at least equalsthe volume of fuel drawn in by the injection pump when priming thelow-pressure pump.

FUEL FEED DEVICE FOR AN INJECTION ENGINE The present invention relatesto fuel feed devices for injection engines.

It is known that the required conditions for ensuring good starting upand good operation of such engines are:

permanent priming of the feed pumps;

rapid removal of gas from the circuit and rapid rise in pres sure uponthe first revolution of the engine;'

fuel fed to the injection pump under constant pressure of the order of lkg./cm and no formation of vapours in the course of operation.

The usual solutions employed are the following:

a. Feeding of the injection pump by a pump driven by an electric motor,which presents several drawbacks. The electropump is costly and theelectric motor, which is highly stressed, creates problems of motorlife.

b. Feeding of the injection pump by a mechanically driven pump, whichalso presents several drawbacks. Owing to its very drive, the positionof the pump is usually rather remote from the tank in a badly cooledregion and, in operation, this results in formation of petrol vapours inthe feed circuit and, upon stoppage, a depriming of the pump.

As the pump is not started up assoon as the engine is switched on butsimultaneously with the starting up of the engine, the rise in pressureis delayed.

The object of the invention is to provide a fuel feed device for aninjection engine which is so improved as to overcome these variousdrawbacks.

The device according to the invention comprises, in series relationbetween a fuel feed tank and the usual injection pump, two mechanicalpumps, one of which is a low-pressure pump and the other a high-pressurepump, driven by the engine, the inlet of the low-pressure pump beingconnected to said tank whereas the outlet thereof is connected to thetop of a chamber affording a pressure head and having a lower fueltakeoff point connected to the inlet of the high-pressure pump whichdischarges the fuel to the injection pump and whose output exceeds thatof said injection pump, the volume of the chamber above the takeoffpoint being at least equal to'the volume of fuel absorbed by theinjection pump during the priming of the low-pressure pump.

This arrangement results in appreciable saving in cost relative toelectric pumps while it satisfies all the conditions for ensuring bothgood starting up and good operation namely:

a permanent priming of the high-pressure feed pump; the vapours in thepart of the circuit upstream of the injection pump are reduced to aminimum; and

a rapid rise in pressure.

Further features and advantages of the invention will be apparent fromthe ensuing description with reference to the accompanying drawing.

In the drawing:

FIG. 1 shows a diagram of the assembly of a fuel feed device for aninjection engine according to the invention; and

FIG. 2 is a sectional view of the valve of this device which results ina rapid rise in pressure.

According to the illustrated embodiment, the invention will be describedas being applied to an internal'combustion injection engine M whoseinjection pump a is driven, for example by a crankshaft b, through atransmission c, this pump injecting petrol into each cylinder d by wayof a pipe e.

The engine M mechanically drives, for example through its camshaft f,simultaneously a low-pressure pump 1 and a highpressure pump 2. Boththese pumps are of atype currently employed in internal combustionengines and they differ from each other only in respect of thedimensions of the diaphragms 3 and the springs 4.

The low-pressure pump 1 draws petrol from a tank 5 through a conduit 6in which is interposed a prefilter 7 consisting for example of a finestrainer of plastics material, this prefilter being placed, if desired,at the inlet of the pump 1 in which it can be incorporated The pump 1delivers the petrol by way of a conduit 8 to the upper part of a chamber9.

The lower part of this chamber constitutes a decantation sump from whichthe impurities can be discharged by way of a drain aperture 10 providedwith a cock-l1, whereas the upper part of the chamber comprises afiltering cartridge 12, for example of paper, through which the petrolmust pass to reach the high-pressure pump 2 by way of a conduit 13,which extends into the chamber up to the base of the filter. The conduit13 must be as short as possible and of suflicient diameter that pressuredrops are negligible. It must not have a part rising in the direction offlow of the fuel.

The chamber 9 must be placed in such manner that it affords a pressurehead relative to the high-pressure pump 2 and its volume above the point14 at which the conduit 13 takes off fuel must be sufiicient to containan amount of fuel exceeding that which the injection pump a would absorbduring the priming of the low-pressure pump 1 when starting up.

Another conduit 15 comprising a constriction 16 extends from the upper.part of the chamber 9 and ensures the return of excess fuel to the tank5. i

The high-pressure pump 2 discharges fuel under pressure by way of aconduit 17' into the injection pump a. lts flow exceeds the consumptionof the engine and the excess fuel returns to the chamber 9 by way of aconduit 18 in which is interposed a check vaLve 19 which opens only whenthe discharge pressure of the high-pressure pump 2 is sufficient, thatis, higher than a given value p, for example 1 kg./cm.

This valve 19 can be constructed for example as shown in FIG. 2. Itmainly comprises a disc 20 biased by a spring 21 with such force thatthe disc remains applied against its seat 22 so long as the pressure ofthe fuel on the upstream side is less than the aforementioned value p,thereby ensuring the operation of the injection pump a.

- A bypass conduit 23, connected to the discharge conduit 17 of thehigh-pressure pump 2, terminates in an electrovalve 24 whichcommunicates with the inlet pipe g of the engine M.

The coil 25 of this electrovalve is electrically fed in parallel withthe starter h of the engine so that it is open only during the period ofoperation of this starter, when the switch 1' is depressed, and closedin normal operation of the engine.

The device operates in the following manner:

When starting up after a period of inactivity, the conduit 13 is alwaysfilled with liquid fuel since if bubbles of fuel vapour have a tendencyto be given off in the course of this inactive period they naturallyrise to the upper part of the chamber 9 whose higher position relativeto the high-pressure pump 2 ensures that the latter is permanentlyprimed. This pump 2 is therefore in a position to discharge fuel to theinjection pump a at the very moment of starting up the engine.

The opening of the electrovalve 24 during the period of operation of thestarter performs a double function:

When starting up in warm conditions, this opening combined with thenegative pressure prevailing at this moment in the inlet pipe 3 ensuresthe rapid discharge of petrol vapours which might have formed inside thehigh-pressure pump 2.

When starting up in cold conditions, this opening enables fuel to beinjected directly in this inlet pump g thus producing a richer mixturewhich facilitates the starting up of the engine.

In any case, the valve 19 maintains the conduit 18 closed so long as thedischarge pressure of the high-pressure pump 2 has not reached the valuep, the rising pressure being possible owing to the fact that the outputof the pump 2 exceeds the fuel drawn off by the injection pump 0.

Operation under conditions of high surrounding tempera ture is notdisturbed by the formation of vapours in the circuit, since the outputof the low-pressure pump 1 and high-pressure pump 2 is distinctly higherthan the consumption of fuel, so much so that the large flow of petrolresults in sufficient cooling. However, if vapours form between the tank5 and the chamber 9, they would not be drawn in by the conduit 13 whosefuel takeoff point 14 is at the base of the filter'l2 but return to thetank 5 by way of the conduit 15 with the unconsumed fuel.

Further, the constriction 16, which retards the return of the fuel tothe tank, maintains a slight pressure in the chamber 9 which retards apossible start of percolation at the inlet of the high-pressure pump 2.

Although a specific embodiment of the invention has been described, manymodifications and changes may be made therein without departing from thescope of the invention.

1 claim: 1. In an internaL combustion engine having a fuel feed tank andan engine driven injection pump, a fuel feed device comprising alow-pressure pump and a high-pressure pump adapted to be driven by theengine, the low-pressure pump having an inlet for connecting to saidtank and an outlet, a chamber affording a pressure head relative to thehigh-pressure pump and having a top part and a lower fuel takeoff point,filter means in said chamber, said outlet being connected to said toppart of said chamber and said fuel takeoff point in said chamber beinglocated at the base of said filter means, said high-pressure pump havingan inlet connected to said fuel takeoff point and an outlet which isconnected to discharge the fuel to the injection pump, the fuel outputof said high-pressure pump exceeding that of said injection pump, thevolume of the chamber above said takeoff point being at least equal tothe volume of fuel drawn in by the injection pump during the priming ofsaid low-pressure pump, and two fuel return conduits connectingrespectively the inlet of the injection pump to the upper part of saidchamber, and the upper part of said chamber to the fuel feed tank, acheck valve being provided in said fuel return conduit connecting theinlet of the injection pump to the upper part of said chamber.

2. A device as claimed in claim 1, wherein restrictor means are providedin said fuel return conduit connecting the upper part of said chamber tothe fuel feed tank.

3. In an internal combustion engine having a fuel feed tank, aninjection pump and an electric starter, a device comprising alow-pressure pump and a high-pressure pump adapted to be driven by theengine, the low-pressure pump having an inlet for connecting to saidtank and an outlet, a chamber affording a pressure head relative to the'high-pressure pump and having a top part and a lower fuel takeoff point,filter means in said chamber, said outlet being connected to said toppart of said chamber and said fuel takeoff point in said chamber beinglocated at the base of said filter means, said high-pressure pump havingan inlet connected to said'fuel takeoff point and an outlet which isconnected to discharge the fuel to the in jection pump, the fuel outputof said high-pressure pump exceeding that of said injection pump, thevolume of the chamber above said takeoff point being at least equal tothe volume of fuel drawn in by the injection pump during the priming ofsaid low-pressure pump, and two fuel return conduits connectingrespectively the inlet of the injection pump to the upper part of saidchamber, and the upper part of said chamber to the fuel feed tank, acheck valve being provided in said fuel return conduit connecting theinlet of the injection pump to the upper part of said chamber, and abypass conduit controlled by an electrovalve which is adapted to beactuated at the same time as the starter of the engine, said conduitconnecting said discharge conduit of said high-pressure pump to theinduction manifold of the engine.

